Process and apparatus for producing synthesis gas through thermochemical conversion of biomass and waste materials

ABSTRACT

The present invention provides a process and apparatus for converting feedstock comprising biomass and/or carbon-containing solid waste material to synthesis gas. The process comprises supplying the feedstock to a gasifier comprising a fluidized bed zone and a post-gasification zone and contacting the feedstock with a gasification agent at a plurality of different operating temperatures based on the ash softening temperature of the feedstock and finally recovering the synthesis gas. The apparatus is configured to perform the process and comprises a plurality of nozzles arranged at an acute angle relative to a horizontal plane of the gasifier.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to EuropeanApplication No. 21150402.2, filed Jan. 6, 2021, incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to processes and apparatuses for theconversion of feedstock comprising biomass and/or carbon-containingsolid waste material to a more useful synthesis gas. In particular, thepresent invention relates to a multi-step process and apparatus forthermochemical conversion, without requiring the use of any externalcatalyst, of such feedstock to synthesis gas. The conversion is achievedthrough contacting the feedstock with at least steam and oxygen in aplurality of steps at different operating temperatures in a controlledand optimized manner to achieve effective conversion to synthesis gas.

BACKGROUND

Waste materials such as municipal solid waste (MSW), agricultural andindustrial waste etc. are mainly landfilled and/or incinerated.Currently, waste recycling is gaining more and more attention, since itallows reuse of a large portion of the already used materials, such aspaper, some plastics, glass, metals etc. However, other non-recyclablematerials are still either dumped into landfills or incinerated in orderto recover some of the chemical energy stored in these materials byconverting it into electricity and heat. This energy, however, cannot bestored.

There is therefore a need for methods and apparatuses which are able tobetter process these other non-recyclable materials.

Gasification of biomass and non-recyclable carbon-containing solid wastematerials converts waste materials into synthesis gas thus providing thepossibility to convert waste into more valuable products, such aschemicals or synthetic fuels. In other words, gasification of wastehelps to recycle the waste materials differently to conventionalrecycling methods by converting the carbon in the waste materials intomore useful molecules (i.e., synthesis gas) which can then besynthesised into valuable final products. Overall, gasifying biomass andwaste materials can bring the following advantages to communities: (1)the utilization of carbon containing solid waste materials in anenvironmentally-friendly process, without emissions of toxic substancesinto the atmosphere (2) providing the most efficient way for convertingthe chemical energy stored in municipal solid waste (MSW) intoelectricity and (3) providing the most efficient way for converting thecarbon content of MSW, resp. refuse derived fuel (RDF), into a highlyvaluable product, such as chemicals or synfuels.

Synthesis gas is typically a fuel gas mixture consisting primarily ofhydrogen, carbon monoxide, and very often some carbon dioxide. It iscommonly used as an intermediate in creating synthetic natural gas andfor producing ammonia or methanol. Synthesis gas (syngas) may beproduced by thermochemical conversion of carbon containing sourcedmaterials, such as forest residues, agricultural residues, industrialand urban waste, etc. In general, the gasification of such carboncontaining sourced materials provide raw synthesis gas which may includeseveral impurities such as sulfur compounds (mainly hydrogen sulfide,H₂S and carbonyl sulfide, COS), ammonia, chlorine compounds (mainlyHCl), volatile matters, lower and high molecular weight tars and fines(mainly in the form of micron and sub-micron fly-ash containing metalsalts), and char particles (carbon contained particulates typicallyabove 500 microns). It is desirable to be able to convert, in anefficient process and apparatus, biomass and other carbon-containingsolid waste materials into more useful synthesis gas products which canthen be used to produce high valuable materials, such as methanol,synthetic natural gas and/or Fischer-Tropsch synthesis fuels.

Various approaches have been devised for producing, purifying, andmodifying raw synthesis gas from carbonaceous materials. These existingapproaches are briefly discussed below.

U.S. Pat. No. 6,063,355 discloses a method for treating waste throughtwo successive fluidized bed and combustion reactors. The solidifiedand/or slurry waste is introduced to the fluidized bed with revolvingflow pattern at a temperature ranging from 450° C. to 650° C., therebyproducing gaseous and carbonaceous materials. These products aredirectly fed to a swirling flow combustion reactor, which is separatefrom the fluidized bed reactor, and increasing the temperature to atleast 1300° C. to produce synthesis gas. The crude syngas produced inthe second reactor is then quenched to separate the slag and thequenched crude syngas is passed through a cyclone and scrubber forfurther cleaning. This method involves the use of two successivefluidized beds which results in higher capital and operational costs.

DE 4317319 A1 discloses a gasification-based technology to produce crudesynthesis gas which is further conditioned and used as a feed foralternative end-products such as methanol, cleaned synthesis gas andhydrogen. The shredded wastes are fed to two parallel connected fixedbed gasifiers wherein the feed is reacted with oxygen, steam and rawcarbon dioxide at temperatures up to 1200° C. The produced crudesynthesis gas is partly sent to an entrained-flow gasifier at atemperature of 1400° C. and pressure of 26 bar (2600 kPa) and partly toa facility consisting of washing, heat recovery and cooling stages,followed by a two-stage gas scrubbing unit, COS hydrolysis and lastlyused for power generation. The produced crude synthesis gas from theentrained-flow gasifier is further processed in a soot wash unit,followed by CO conversion, gas cooling and scrubbing units and finallyused for producing methanol. Again, the use of two parallel fixed bedgasifiers and one entrained flow gasifier results in higher capital andoperational costs.

EP 2376607 B1 discloses a method for producing and treating crude syngasfrom biomass through a three-step gasification and reforming process atpressure lower than 10 atm (1013 kPa). The solid biomass is fed to thebottom section, described as a gasification zone, of a fluidized bedreactor in the presence of oxygen and steam, wherein the temperaturelies within the range of 500° C. to 750° C. (in the first step). Theportion of said oxidized biomass produced in the first step is directlytreated in a freeboard region with a residence time lower than 8 s inthe presence of oxygen and steam at temperatures ranging from 800° C. to850° C. (in the second step). The portion of said oxidized biomassproduced in the second step is then treated in a separate thermalreformer with oxidizing gas comprising oxygen and steam at a temperatureof at least 900° C. and not exceeding a maximum of 1000° C. to producecrude syngas (in the third step). The crude syngas produced in thethermal reformer is then passed through a cyclone, followed by a heatrecovery unit and finally scrubbers for further cleaning. This methodhas a number of disadvantages, such as:

-   -   the third step takes place in a separated thermal reformer        apparatus which means that an additional reactor is required,        leading to higher capital and operational costs;    -   the method is restricted to the operating pressure of the        gasifier, which is below 10 atm (1013 kPa). This results in        larger gasifier unit sizes being required when processing larger        quantities of feedstock;    -   due to shorter residence times in the post-gasification zone,        heavier hydrocarbons are not completely decomposed and therefore        a subsequent separate thermal reforming unit is required (as        mentioned above); and    -   the reliance on using external catalysts and bed material for        gasification increases the operational costs of the system.

US 2005/0039400 A1 discloses a method and apparatus for producingsubstantially pure hydrogen from carbonaceous materials using ahydrogen-selective permeation membrane incorporated into two successivegasification and/or gas-phase reactors. The carbonaceous feedstock isfed to a membrane gasifier wherein the gasification agents areintroduced from the bottom of the reactor, providing fluidization andreaction within the system, working at temperatures typically in a rangeof 700° C. to 2000° C. and pressures in a range of 1 to 200 atm (101 to20265 kPa). The produced crude syngas is contacted with a specialpermeable hydrogen selective membrane to separate pure hydrogen from theretentate. The effluent syngas from the gasifier is passed through asuccessive fuel reforming process in a shift reactor equipped withhydrogen-selective permeation membrane, in which substantially purehydrogen is produced and separated from the crude syngas. The retentatecrude syngas is further treated and cleaned in a gas cleaning and CO₂removal unit. This process requires very high operating temperatures upto 2000° C. and very high operating pressures of up to 200 atm (20265kPa), which increases the total capital cost and operating costs.Incorporating membranes into the reactors can also cause problems duringoperation such as clogging of membranes due to the high ash content ofproduced crude synthesis gas. Using membranes in the gasifier alsoimposes considerable maintenance services during operation leading to ahigher operational cost.

DE 10 2017 219 783 A1 discloses a HTW gasifier device.

DE 195 48 324 A1 discloses a process for the gasification ofcarbonaceous solid materials.

WO 2018 095 781 A1 relates to a system for converting carbon-containingfuels into synthesis gas.

DE 2 949 533 A1 is concerned with a solid fuel fluidized bed reactorwith a uniform temperature in a secondary reaction zone above the bed byspaced reagent injection.

There therefore exists a need for processes and apparatuses which areable to convert feedstock comprising biomass and/or carbon-containingsolid waste material to synthesis gas in a more efficient, convenientand cost-effective manner.

In this respect, it has been discovered by the inventors of the presentinvention that the principles of High Temperature Winkler (HTW)technologies can be adapted in order to provide a process and apparatusthat efficiently converts biomass and/or carbon-containing solid wastematerial into synthesis gas. HTW gasification is a long establishedmethod performed at elevated pressures and can be described as apressure-loaded fluidized bed gasification process. The HTW method wasused originally for a broad range of applications but, up until now,there have been difficulties in developing existing HTW technologies inorder to efficiently convert biomass and/or carbon-containing solidwaste materials into synthesis gas.

SUMMARY

In an aspect of the invention, there is provided a process forconverting feedstock comprising biomass and/or carbon-containing solidwaste material to synthesis gas, the process comprising the followingsteps:

(a) supplying the feedstock to a gasifier, the gasifier comprising afluidized bed zone and a post-gasification zone;(b) contacting the feedstock with a gasification agent comprising steamand oxygen in the fluidized bed zone, at an average temperature ofbetween about 350-400° C. below the ash softening temperature of thefeedstock, to partially oxidize the feedstock;(c) contacting at least a portion of the partially oxidized productproduced in step (b) with a gasification agent comprising steam andoxygen in the fluidized bed zone, at a higher average temperature thanin step (b), the average temperature being between about 250-350° C.below the ash softening temperature of the feedstock;(d) contacting at least a portion of the product produced in step (c)with a gasification agent comprising steam and oxygen in thepost-gasification zone, at a higher average temperature than in step(c), the average temperature being between about 200-300° C. below theash softening temperature of the feedstock;(e) contacting at least a portion of the product produced in step (d)with a gasification agent comprising steam and oxygen in thepost-gasification zone, at a higher average temperature than in step(d), the average temperature being between about 150-250° C. below theash softening temperature of the feedstock, to produce the synthesisgas; and(f) recovering the synthesis gas from the product produced in step (e).

The process according to the invention provides a simple, relatively lowcost and efficient way of converting feedstock comprising biomass and/orcarbon-containing solid waste material to synthesis gas. The use of asingle gasifier comprising both a fluidized bed zone andpost-gasification zone greatly simplifies the process compared withthose prior art processes that rely on the use of multiple units e.g., areactor and a complimentary reformer/combustor. It has also been foundthat the above operating temperatures provides effective conversion ofthe feedstock to syngas and also allows flexibility in terms of theother operating conditions in the gasifier, such as pressure. Inparticular, the present process permits the use of higher pressures, upto approximately 3000 kPa, which allows the use of small size units andmore compacted units for higher product capacity. Furthermore, highergasification pressures are favourable for the downstream processes, suchas synthesis of methanol, synthetic natural gas or ammonia from theproduced syngas—which all require high pressures. Thus, less energy isrequired to operate the downstream processes due to the higher pressuresof the raw syngas from the gasifier. The process steps can also beconveniently controlled along the fluidized bed and post-gasificationzones, allowing optimisation of conditions depending on thecharacteristics of the feedstock.

In an embodiment, the process further comprises a step of cooling atleast a portion of the product produced in step (e) to an averagetemperature lower than in step (e), the average temperature being nogreater than about 200° C. below the ash softening temperature of thecarbonaceous feedstock, wherein this step takes place in thepost-gasification zone.

In an embodiment, the cooling step takes place in a quench subzone, inparticular at the upper part, of the post-gasification zone and the stepof cooling is performed using quench water or process condensate.

The above two embodiments quench the raw syngas, thus freezing orquenching sticky particles that were formed in the higher temperaturesof the process, and thereby minimize the relevant problems mainlyincluding clogging in downstream process equipment, which thus increasesthe gasifier availability. Thus, due to a high temperature and thepossibility of melting the inorganic material in the entrained char suchas alkali chloride and metal oxides, the raw syngas is subjected to thequench subzone so as to minimize the agglomeration problems ordeposition of melted materials on the walls in the post-gasificationregion and downstream units such as the cyclone and raw gas cooler.

In an embodiment, the process further comprises a step of removing atleast a portion of a bottom product, optionally a heavy solid residue,produced in step (b) to a sedimentation subzone in the fluidized bedzone.

In an embodiment, the process further comprises treating the bottomproduct in the sedimentation subzone with a gasification agentcomprising steam and/or CO₂, optionally wherein the treatment is carriedout at an average temperature lower than in step (b), the averagetemperature being not greater than about 400° C. below the ash softeningtemperature of the feedstock. The use of steam and/or CO₂ in thesedimentation subzone helps to fluidize the bed material around anygasification agent entry points in the lower regions of the fluidizedbed zone in order to avoid hot spots and channels developing in-front ofthese entry points.

In an embodiment, step (f) comprises feeding at least a portion of thesynthesis gas to a cyclone and separating the produced synthesis gasfrom entrained particulate material, optionally fly-ash or char, andrecycling at least a portion of the particulate material back to step(b) in the fluidized bed zone.

In a certain embodiment, the residence time in the fluidized bed zone isat least about 8 minutes and the residence time in the post-gasificationzone is at least about 7 seconds.

In one embodiment, the residence time of raw synthesis gas in thepost-gasification zone is at least about 7 seconds. A residence time, ofe.g. raw synthesis gas, of at least about 7 seconds in thepost-gasification zone improves the thermal decomposition of the heavierhydrocarbons including tars. The process can therefore advantageouslyproduce tar-free synthesis gas.

In an embodiment, the process comprises providing the gasificationagents through a plurality of nozzles, optionally tuyeres, wherein thenozzles are arranged at an acute angle relative to a horizontal plane ofthe gasifier.

In an embodiment, the process further comprises operating the gasifierat a pressure of about 1000 kPa to 3000 kPa, optionally wherein thegasifier is a refractory lined reactor.

In an embodiment, the process further comprises operating the gasifierwithout adding external bed material and catalyst. The process canoperate without requiring the addition of external catalyst. This isbeneficial in reducing operating costs and making the process simpler tooperate because added external catalyst can get poisoned quickly (inparticular from impurities present in the feedstock) as well as beingdifficult to handle and reuse.

In an embodiment, the process further comprises supplying thegasification agent to the gasifier so that the oxygen content in thegasifier is in the controlled range of 0.28-0.52 Nm³/kg (daf) of thefeedstock, of which at least about 20% and not greater than about 80% issupplied to the fluidized bed zone and so that the amount of steam inthe gasifier is in the controlled range of 0.23-0.52 Nm³/kg (daf) of thefeedstock, of which at least about 40% and not greater than about 80% issupplied to the fluidized bed zone.

In an embodiment, the supplied feedstock is a pelletized feedstock,optionally further comprising pressurizing the pelletized feedstock in apressurisation system prior to supplying the feedstock to the fluidizedbed zone in step (b). The use of a pelletized feedstock is favourable atelevated pressures and also provides a feedstock with higher carbondensity than shredded or non-pelletized material.

In an embodiment, the post-gasification zone is arranged in the gasifierabove the fluidized bed zone, wherein the fluidized bed zone is in aconical portion of the gasifier.

In an embodiment, the process further comprises performing each of steps(b) to (e) in substantially separate subzones within the gasifier.

Also disclosed herein is an apparatus for performing the processaccording to the previous aspect or any of the embodiments above,wherein the apparatus comprises a gasifier, wherein the gasifiercomprises a fluidized bed zone and a post-gasification zone; and aplurality of nozzles, optionally tuyeres, within the gasifier, whereinat least one of the nozzles is arranged at an acute angle relative to ahorizontal plane of the gasifier and wherein the plurality of nozzlesare configured to supply in use the gasification agent so as to generateboth the required fluidisation inside the fluidized bed zone and theplurality of operating temperatures within the fluidized bed andpost-gasification zones of the gasifier.

The use of such nozzles enhances localized transport and reactionmechanisms along the gasifier. In particular, the nozzle arrangementhelps to optimise conditions within the gasifier by enhancing thecracking of undesirable high molecular weight hydrocarbons such asheterocyclic compounds, aromatic compounds and light and heavypolycyclic aromatic compounds—as compared with typical nozzles which arearranged in a horizontal plane of the gasifier and typically inject thegasification agent along a substantially horizontal plane into thegasifier. The hereinabove mentioned high molecular weight hydrocarbonsare undesirable in the product synthesis gas and thus the quality of thesynthesis gas product is improved.

Also provided herein as examples useful for understanding the inventionis:

a process for converting feedstock comprising biomass and/orcarbon-containing solid waste material to synthesis gas, the processcomprising supplying the feedstock to a gasifier, the gasifiercomprising a fluidized bed zone and a post-gasification zone andcontacting the feedstock with a gasification agent comprising steam andoxygen in the fluidized bed and post-gasification zones, to producesynthesis gas; wherein the process further comprises any of thefollowing features on their own or in any combination:

-   -   wherein the supplied feedstock is a pelletized feedstock,        optionally further comprising pressurizing the pelletized        feedstock in a pressurisation system prior to supplying the        feedstock to the fluidized bed zone in step (b); and/or    -   providing the gasification agents through a plurality of        nozzles, optionally tuyeres, wherein at least one of the nozzles        is arranged at an acute angle relative to a horizontal plane of        the gasifier, further optionally wherein the nozzles are        multilayered; and/or    -   further comprising operating the gasifier at a pressure of about        1000 kPa to 3000 kPa, optionally wherein the gasifier is a        refractory lined reactor; and/or    -   wherein the residence time, e.g. of raw synthesis gas, in the        post-gasification zone is at least about 7 seconds.

Also provided herein as an example useful for understanding theinvention is an apparatus for converting feedstock comprising biomassand/or carbon-containing solid waste material to synthesis gas, theapparatus comprising any one or more of the following:

-   -   means for supplying the feedstock to a gasifier;    -   a gasifier comprising a fluidized bed zone and a        post-gasification zone;    -   at least one nozzle, for supplying a gasification agent to the        gasifier, arranged at an acute angle relative to a horizontal        plane of the gasifier, optionally a plurality of nozzles        arranged as such;    -   a plurality of nozzles, for introducing gasification agent to        the gasifier, arranged so as to generate in use a plurality of        temperature subzones within the gasifier, optionally wherein the        plurality of nozzles are arranged along the sides of the        gasifier;    -   a plurality of nozzles, for introducing gasification agent to        the gasifier, arranged so as to generate fluidization within the        fluidized bed zone of the gasifier; and/or    -   means for recovering the syngas downstream of the gasifier.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the present invention are shown in theaccompanying drawing and hereinafter described in detail.

FIG. 1 shows an example process and apparatus arrangement for convertingfeedstock comprising biomass and/or carbon-containing solid wastematerial to synthesis gas according to an embodiment of the invention.

FIG. 2 shows an exemplary temperature profile in an apparatusarrangement such as shown in FIG. 1 when carrying out a processaccording to the present invention.

DETAILED DESCRIPTION

Processes and apparatuses for the conversion of feedstock comprisingbiomass and/or carbon-containing solid waste material to synthesis gasare provided herein and in accordance with the present claimed inventionto resolve the foregoing problems in prior art processes andapparatuses.

An embodiment of the process and apparatus of the present invention isshown in FIG. 1.

In FIG. 1, a pelletized biomass and/or carbon-containing solid wastematerial feedstock is fed into the system via line 1, through lockhopper system 101 and via line 2 to feed screw conveyer 102 at elevatedpressures through line 3 into a lower section of the fluidized bed zone116 of gasifier 103. Gasifier 103 has a fluidized bed zone 116 and apost-gasification zone 117 above (downstream from) the fluidized bedzone 116. Subzones A, B and C are within the fluidized bed zone 116,while subzones D, E and F are within the post-gasification zone 117. Thepelletized feedstock is introduced into the gasifier at subzone B, theso-called solid entry fluidized bed zone, in FIG. 1.

Gasification agent comprising steam and oxygen (and also optionallycarbon dioxide) is fed to gasifier 103 through line 4 a. In FIG. 1, itis shown that the gasification agent is introduced into the gasifier 103via the fluidized bed zone 116, although in reality the gasificationagent will be introduced at various different points along the gasifier103, as will be explained later on in more detail.

Although not shown in FIG. 1, the gasification agent is introduced intothe gasifier 103 via controlled flowrate through specializedmultilayered nozzles. The form and amount of gasification agentintroduced into the gasifier 103 will depend on the properties of thefeedstock to be gasified. Typically the gasification agent is suppliedto the gasifier so that the oxygen content in the gasifier is in thecontrolled range of 0.28-0.52 Nm³/kg (daf) of the feedstock, of which atleast about 20% and not greater than about 80% is supplied to thefluidized bed zone. In further embodiments, the gasification agent issupplied to the gasifier so that the oxygen content in the gasifier isin the controlled range of 0.35-0.45 Nm³/kg (daf) of the feedstock, ofwhich at least about 35% and not greater than about 65% is supplied tothe fluidized bed zone. The temperature of the subzones is dependent onthe ash softening temperature of the feedstock. The temperature of eachsubzone is achieved through the content, properties and amount ofgasification agent (comprising at least oxygen and steam) added to thegasifier. An external heat source does not need to be used and inpreferred embodiments is not used.

The feedstock is treated through the fluidized bed zone 116 andpost-gasification zone 117 of the gasifier 103 by travelling and beingtreated through subzones B, C, D, E and F (with the bottom product beingtreated in subzone A and instead leaving via the bottom of the gasifier)before leaving the gasifier as a raw syngas product via line 8.

In subzone B, termed here as the solid entry fluidized bed zone, thepelletized feedstock is partially oxidized by the gasification agentcomprising oxygen and steam. The gasification agent supply is controlledsuch that the average temperature of subzone B is within the range of350-400° C. below the ash softening temperature of the pelletizedfeedstock. Prior to carrying out the process the ash softeningtemperature of the pelletized feedstock is calculated and the supply ofthe gasification agent throughout the gasifier adjusted accordingly.

In subzone B of the fluidized bed zone 116, some of the feedstock incontact with hot fluid bed particles heats up and due to thermalexpansion and physical abrasion decomposes on small pieces that aftercontacting the gasification agents decompose thermally, going throughdrying, pyrolysis and char-oxidation processes thereby producing heavymoderate-to-low carbon content residue that accumulates in subzone A ofthe fluidized bed zone 116 i.e., the sedimentation subzone. The averagetemperature in subzone A (the sedimentation zone) is lower than theaverage temperature in subzone B and is between 400-500° C. below theash softening temperature of the feedstock. In the sedimentation subzonethe bottoms product is treated with a gasification agent comprisingsteam (and CO₂).

In subzone A, heavy solid carbonaceous residue settles down and leavesthe gasifier via the bottom of the fluidized bed zone (through lines 5 aand 5 b). A basic fluidization agent, normally inert gas, is injected atthe bottom of subzone A, providing a fluidization velocity ranging from0.5 to 1.6 m/s depending on the bottom product physical properties. Vialines 5 a and 5 b, the heavy residue is processed through lock hoppers105, and then via lines 6 a and 6 b to bottom product removal unit 106before leaving via line 7 c to be used in the cement industry or vialine 7 b to auxiliary boiler 107, wherein high pressure steam isproduced and the residual ash generated can be used in the cementindustry.

In subzone B, a partially oxidized produced gas containing low and highmolecular weight hydrocarbons in the form of volatiles and heterocycliccompounds (e.g., phenol, cresol, quinoline, pyridine), together withlight aromatic compounds (e.g., toluene, xylems, ethyl benzene), andlight polyaromatic hydrocarbons (e.g., naphthalene, indene, biphenyl,anthracene), along with unreacted parts of the gasification agent, risesfrom subzone B to the upper most subzone of the fluidized bed zone 116,subzone C, termed here as the highly fluidized bed subzone.

Again, the supply of gasification agent to subzone C is controlled byproperties of the pelletized feedstock and the oxygen and steamgasification agent is supplied such that the average temperature insubzone C is higher than in subzone B and 250-350° C. below the ashsoftening temperature of the feedstock. This condition provides anoptimum temperature gradient along the reactor in the highly fluidizedbed zone (subzone C) in which the produced gas from subzone B, in theform of heavy fly char loaded gas bubbles, is further decomposed andtransformed thermally into a raw product gas with a higher fraction oflower molecular weight hydrocarbons.

In the fluidized bed zone 116, the pelletized carbon containingfeedstock and the generated carbon content residue is contacted withfluidization agent for a time period of at least 8 minutes to ensure ahigh degree of completion for partial oxidation and homogenous andheterogenous thermal decomposition reactions.

The pelletized carbon containing feedstock in the fluidized bed zone 116gets partially oxidized and thermally decomposed to produce carbonmonoxide and hydrogen, and volatiles of majorly lower molecular weighthydrocarbons together with intermediate species in the form ofheterocyclic compounds, light aromatics, light polyaromatichydrocarbons, unreacted part of the gasification agent, and entrainedfly ash/char particles and then passes to the post-gasification zone 117of the gasifier 103. The fly ash/char particles, still contain highcarbon concentration have inorganic materials, such as alkali chlorides,metal oxides, etc. in the form salts. Fly ash/char particles are usuallyless than 200 microns in size, and therefore rise to thepost-gasification zone 117. In the post-gasification zone 117, thepartially oxidized material is contacted with gasification agentcontaining oxygen and steam (and sometimes CO₂) for a period of at least7 s through three successive thermal subzones which are elaboratedhereafter.

The thermochemically transformed material from the fluidized bed zone116 enters the post-gasification zone 117 through subzone D, termed hereas, heavily loaded solid fly ash/char subzone, wherein the temperatureis adjusted through a controlled supply of gasification agent of steamand oxygen such that the average temperature is higher than in subzone Cand is 200-300° C. below the ash softening temperature of the feedstock.In subzone D, the carbon present in the fly char is further convertedthermochemically in the presence of steam, CO₂ and oxygen therebyachieving a high carbon conversion efficiency. In parallel, theintermediate gaseous hydrocarbons produced in subzone C undergo crackinginto simpler molecules such as carbon monoxide and hydrogen.

The reformed and oxidized raw gas then enters subzone E in thepost-gasification zone 117, termed here as, low fly ash loaded subzone,where the steam and oxygen gasification agent supply is controlled suchthat the average temperature of subzone E is higher than in subzone Dand 150-250° C. below the ash softening temperature of the feedstock.Subzone E is characterized by further conversion of carbon present inthe char particles and even further decomposition of intermediatehydrocarbons and tars present in the form of heterocyclic compounds,light aromatics, and light polyaromatic hydrocarbons. High temperaturesin low fly ash loaded subzone (subzone E) allows for even better carbonconversion efficiency due to enhanced gasification reactions whichimproves the carbon conversion.

The raw syngas product from subzone E is passed through the topmostsection of the gasifier, subzone F, termed here a quench subzone. Thissubzone is still within the post-gasification zone 117 of the gasifier103. In subzone F, the raw syngas is treated at an average temperatureof about 200° C. to 250° C. below the ash softening temperature of thefeedstock and at an average temperature lower than in subzone E. In thissubzone, the raw syngas is cooled using quench water or processcondensate, which is sufficient to lower the average temperature belowthe ash softening point. This quenches the raw syngas thus freezing orquenching sticky particles formed in the higher temperatures and helpsto minimize agglomeration problems or deposition of melted materials onthe walls in the post-gasification zone 117 and downstream units such asthe cyclone 104 and the raw gas cooler (108).

The cooled raw syngas is then withdrawn from the gasifier 103 throughline 8 and passed through a cyclone 104, in which approximately >95% ofthe entrained dust is separated and recycled back through line 9 to thefluidized bed zone 116 of the gasifier 103. In general, recycling suchparticles which comprise of inorganic compounds coated with carbon canimprove the overall carbon conversion efficiency by increasing theresidence time of the fly ash/char particles in the gasifier.

The tar free syngas is withdrawn from cyclone 104 via line 10 and passesthrough raw gas cooler 108 to produce saturated steam. Part of the steamcan be re-used in the process by going via line 11 to superheater 115and the superheated steam recycled to the gasifier 103 via line 12. Thecooled syngas with a minimum temperature of 250° C. is subjected tofurther processing, enhancement, and purification including filtering inthe fly-char dry based removal unit 109 through line 13, wherein thedust with the particle size greater than 5 microns is filtered and as aby-product can be sent to either feedstock pelletizing unit 114 (throughline 15 a) or the cement industry (through line 15 b) via lock hopper110 and dust removal unit 111. Through line 16 to quench and scrubbingunit 112 (including lines, 17, 18, 18 a and 19) where (a) the tar freesyngas is saturated which is a favourable condition for downstreamprocessing, e.g. CO shift and COS hydrolysis, and (b) the impuritiessuch as hydrogen chloride are absorbed in alkali solution, while otherimpurities including H₂S, COS, NH₃, HCN, etc. are partially eliminatedby adjusting the pH of the alkali solution. The sour water from thequench and scrubbing unit 112 is sent to the waste-water treatment unit113 (through line 18 b) for further stripping and treatment. The finalsyngas product is then obtained from the quench and scrubbing unit 112.

The gasification agent is introduced into the gasifier at various entrypoints throughout the fluidized bed zone 116 and the post-gasificationzone 117. The optimized conditions throughout the gasifier are aidedthrough the use of specialized, multilayered nozzles (not shown inFIG. 1) that introduce the gasification agent into the gasifier at anacute angle relative to a horizontal plane. The gasification agent issupplied in sufficient quantity and content to partially oxidize andthermochemically decompose the pelletized feedstock to high quality, tarfree syngas. As will be understood by the person skilled in the art, theconditions within the gasifier may also be further optimized based onthermochemical properties of the pelletized feedstock, such as fixedcarbon content, heating value, metal content and other impurity levelsetc.

The temperature profile shown in FIG. 2 is in accordance with thetemperatures used in the process according to the present invention. Thetemperature profile of FIG. 2 is usually used when operating a gasifier103 shown in FIG. 1. The symbol “T_(ASP)” used in FIG. 2 denotes thetemperature at the ash softening point. Therefore, subzone A of FIG. 2corresponds to subzone A of FIG. 1. In subzone A of FIG. 2, the heavy,ash-containing particles accumulate in the lower part of the fluidizedbed before they leave the gasifier 103, and are discharged as a bottomproduct. Subzone A is used to form a bottom product with low carboncontent, which is important to achieve sufficient carbon conversion inthe gasifier 103. The temperatures in this area can be in the range of400° C. to 500° C. below the ash softening temperature of the feedstock,because the injected gas in this area is usually only steam, CO₂ orrecycled syngas. To avoid local ash softening, no oxygen-containinggasifying agent is usually added to this slightly fluidized zone. Theaverage temperature of 400° C. to 500° C. below the ash softeningtemperature of the feedstock results from a constant exchange of solidswith the hotter parts of the fluidized bed above this subzone.

Subzone B of FIG. 2 is the area where the feedstock is introduced intothe gasifier 103. The average temperature in subzone B is higher than insubzone A and in the range between 350° C. to 400° C. below the ashsoftening temperature of the feedstock, in order to decompose the higherhydrocarbons that are released during the drying and the pyrolysis ofthe feedstock as soon as possible. In this already well-fluidized zoneof the fluidized bed, the first oxygen-containing gasifying agent isadded.

In subzone C of FIG. 2, the upper part of the fluidized bed is very wellfluidized due to the raw gas produced inside the fluidized bed and dueto the higher fraction of fine particles. This subzone is characterizedwith a higher amount of oxygen (gasification agent) supplied throughnozzles that are located in the post-gasification zone 117, but directeddownwards to the fluidized bed. The average temperature in this subzoneis higher than in subzone B and around 250° C. to 350° C. below the ashsoftening temperature of the feedstock.

Subzone D of FIG. 2 begins directly above the fluidized bed. It has awide range of solid particles, which are ejected from the fluidized bedand partly fall back into the fluidized bed. A further oxygen supply(e.g. by a nozzle) in this subzone D is carried out which achieves ahigh carbon conversion. The average temperature is higher than insubzone C and 200° C. to 300° C. below the ash softening temperature ofthe feedstock.

Subzone E of FIG. 2 represents gasification zone with low solidscontent. Due to the significantly lower solids content and throughadditional oxygen supply (e.g. by a nozzle) at the lower part of thissubzone, the temperatures in this area rise up to an average temperaturebeing higher than in subzone D and which is between 150° C. and 250° C.below the ash softening temperature of the feedstock, which leads to afurther carbon conversion that takes place. According to the Boudouardequilibrium, the higher temperatures in this zone allow to achievehigher amounts of CO formed in the raw gas thus improve the syngasyield. Additionally, unwanted hydrocarbon components, such as methane,benzene and naphthalene, in the raw gas can be significantly reduced.Further, due to the endothermic gasification reactions, the averagetemperature of raw syngas and of the entrained particulate mattergradually reduces by approaching the gasifier outlet.

Subzone F shown in FIG. 2 is also denoted as a quench zone. In subzoneF, the raw syngas is treated at an average temperature of about 200° C.to 250° C. below the ash softening temperature of the feedstock and atan average temperature lower than in subzone E. By injecting boiler feedwater or process condensate at the top of the gasifier, the temperaturecan be reduced additionally by up to 50° C. in this area. This coolingof the raw gas is sufficient to cool softened ash components, if any, sofar that in the gas transition to the cyclone 104 and in the downstreamsystems there will be essentially no more sticky ash components.

The process and apparatus of the invention will now be described in moredetail.

Process for Conversion of Feedstock Comprising Biomass and/orCarbon-Containing Solid Waste Material to Synthesis Gas

The process of the present invention for converting feedstock comprisingbiomass and/or carbon-containing solid waste material to synthesis gas,generally comprises the following steps:

(a) supplying the feedstock to a gasifier, the gasifier comprising afluidized bed zone and a post-gasification zone;(b) contacting the feedstock with a gasification agent comprising steamand oxygen in the fluidized bed zone, at an average temperature ofbetween about 350-400° C. below the ash softening temperature of thefeedstock, to partially oxidize the feedstock;(c) contacting at least a portion of the partially oxidized productproduced in step (b) with a gasification agent comprising steam andoxygen in the fluidized bed zone, at a higher average temperature thanin step (b), the average temperature being between about 250-350° C.below the ash softening temperature of the feedstock;(d) contacting at least a portion of the product produced in step (c)with a gasification agent comprising steam and oxygen in thepost-gasification zone, at a higher average temperature than in step(c), the average temperature being between about 200-300° C. below theash softening temperature of the feedstock;(e) contacting at least a portion of the product produced in step (d)with a gasification agent comprising steam and oxygen in thepost-gasification zone, at a higher average temperature than in step(d), the average temperature being between about 150-250° C. below theash softening temperature of the feedstock, to produce the synthesisgas; and(f) recovering the synthesis gas from the product produced in step (e).

As will be understood by a person skilled in the art, unless prohibitedexplicitly by the wording of the steps, there may be further additionalsteps performed between steps (a) to (f). As will also be understood,the synthesis gas product in step (e) will usually be in the form of rawsynthesis gas (or syngas) and a number of purification steps may need tobe performed into order to convert the raw syngas into a quality syngasproduct which is usable.

Feedstock

The feedstock comprising biomass and/or carbon-containing solid wastematerial is fed into the fluidized bed zone of the gasifier. Thefeedstock may be fed to the fluidized bed zone via a lock hopper systemand feed screw conveyer at elevated pressures. The feed system (notshown in detail in FIG. 1) may include a series of lock hoppers, starfeeders and screw conveyers which are pressurized with CO₂. In certainembodiments, the CO₂ is separated from the raw syngas during downstreamprocessing in methods known in the art. In certain embodiments, theseparated CO₂ is reused as a pressurizing agent in the feed system toenable the feeding system to operate at the similar pressure as thegasifier.

Alternatively, any suitable apparatus for feeding the feedstock to thefluidized bed zone of the gasifier can be used.

Any suitable feedstock comprising biomass and/or carbon-containing solidwaste material is suitable to be processed in the process of the presentinvention. In alternative embodiments the feedstock comprises biomass.In an alternative embodiment the feedstock comprises a carbon-containingsolid waste material. In some embodiments, the feedstock comprises onlybiomass, in other embodiments only carbon-containing solid wastematerial and in further embodiments comprises a blend of biomass andcarbon-containing solid waste material.

The process of the present invention is able to process homogenous andheterogeneous feedstocks. In certain embodiments the feedstock is ahomogenous feedstock. In other embodiments the feedstock is aheterogeneous feedstock. The term “homogenous feedstock” refers tosingle-sourced material e.g., trees, agricultural residues, wood chips.“Heterogeneous feedstock” refers to multi-sourced materials e.g.,materials such as wood residues from sawmills, textiles, paper, plastic,cardboard, hydrocarbon compounds and contaminants compounds.

Biomass refers to materials typically classed as biomass i.e., organicmatter. Examples of biomass that may be used in the invention are woodand plants. Carbon-containing solid waste material is defined as anyform of solid waste which comprises material that is carbon-containing.Examples of carbon-containing solid waste include wastes such as woodwaste, agricultural waste, municipal solid waste (MSW), refuse derivedfuels (RDF), dried sewage sludge and industrial waste. The abovematerials may be processed in the invention alone or in combination withone another in a blend. Preferred feedstocks include: RDF, MSW, wastewood (preferably untreated) and hard wood, all of which may be processedalone or in combination with one another. In particular, preferredfeedstocks are selected from RDF alone, MSW alone, RDF and MSW blend,RDF with plastic, untreated wood and hard wood. Particularly preferredis the use of an RDF and MSW blend.

Various different feedstocks that comprise biomass and carbon-containingsolid waste material, and in various different forms, are suitablefeedstocks in the present process. Particularly preferred, however, isthe use of a pelletized feedstock. Any suitable pelletizing method knownin the art may be used. The pelletized feedstock is preferablypressurized in a pressurisation system prior to being supplied to thegasifier. The use of a pelletized material is not only favourable forgasification processes at elevated pressures but also provides afeedstock with higher bulk density than shredded or non-pelletizedmaterial. The use of pelletized flow material facilitates operation athigh pressures achieving two main advantages, namely the higher feeddensity leads to lower CO₂ consumption which is advantageous for theprocess and improving the flowability of the feed material which can beimportant when using lock hopper gravity system for pressurization.Furthermore, there is a possibility to mix the moderate-to-high carboncontent dust, removed from the process with pelletized feedstock, andthereby increasing the overall carbon conversion efficiency of thesystem. There is a possibility to premix minor amounts of additivesincluding but not limited magnesium compounds to neutralize impuritiessuch as chorine, fluorine and sulphur which are inherently present inpelletized carbon containing material.

Gasification Agent

The gasification agent comprises oxygen and steam. In certainembodiments, the gasification agent further comprises any other suitablegasification agent. In certain embodiments, the gasification agentfurther comprises air. In certain embodiments the gasification agentfurther comprises CO₂. In certain embodiments, the gasification agent isoxygen and steam i.e., the gasification agent does not comprise anyother substantial gas (with the exception of impurities). Preferably,the gasification agent is either oxygen and steam or oxygen, steam andair, most preferably oxygen and steam. In possible alternativeembodiments, the gasification agent is air. The gasification agent isfed into the fluidized bed zone of the gasifier using any suitablefeeding means.

It is preferred that the gasification agent is introduced into thegasifier via a controlled flowrate, optionally through a single ormultilayered nozzle system, as is described in more detail herein.

In some embodiments, the content of the gasification agent and theamount of gasification agent introduced into the gasifier will depend onthe quality of the feedstock and its characteristics and properties. Insome embodiments, this includes properties of the feedstock such as thefixed carbon content, heating value, ash melting point, and metalcontent and other impurity levels. In certain embodiments, the contentand amount provided should be sufficient to partially oxidize andthermochemically decompose the feedstock to high quality, tar freesyngas, as will be understood in the art. Ultimately, in preferredembodiments the gasification agent is selected so as to be sufficient toconvert the feedstock to raw syngas.

In certain embodiments, subject to the specific feedstock that is usedin the process, the gasification agent is supplied to the gasifier sothat the oxygen content in the gasifier is in the controlled range of0.28-0.52 Nm³/kg (daf) of the feedstock, of which at least about 20% andnot greater than about 80% is supplied to the fluidized bed zone. Infurther embodiments, the gasification agent is supplied to the gasifierso that the oxygen content in the gasifier is in the controlled range of0.35-0.45 Nm³/kg (daf) of the feedstock, of which at least about 35% andnot greater than about 65% is supplied to the fluidized bed zone.

daf or DAF=Dry Ash Free content, the weight percentage from the dry andash free material, is calculated as follows:

daf=100/(100−TM−ash)

where, TM=total moisture content of the feedstock, ash=ash content inthe feedstock. TM is calculated using ISO 18134-1 and ash content usingISO 18122 standard.

In certain embodiments, subject to the specific feedstock that is usedin the process, the gasification agent is supplied to the gasifier sothat the amount of steam in the gasifier is in the controlled range of0.23-0.52 Nm³/kg (daf) of the feedstock, of which at least about 40% andnot greater than about 80% is supplied to the fluidized bed zone. Infurther embodiments, subject to the specific feedstock that is used inthe process, the gasification agent is supplied to the gasifier so thatthe amount of steam in the gasifier is in the controlled range of0.30-0.45 Nm³/kg (daf) of the feedstock, of which at least about 50% andnot greater than about 70% is supplied to the fluidized bed zone.

Operation of the Gasifier

The gasifier comprises a fluidized bed zone and a post-gasification zonei.e., both zones are present in a single reactor (i.e., gasifier). Incertain embodiments, the fluidized bed zone is below thepost-gasification zone. A fluidized bed zone takes its usual meaning inthe art and in HTW gasification, namely a bed of material in which theproperties during operation are such that the material therein behavesas a fluid. In certain embodiments, the bubbling fluidized bed includesinternally produced solid remnants of gasified feedstock, termed here asbed material. In general, the bed materials have a particle size rangingfrom about 200 to about 1600 microns.

The post-gasification zone as used herein also takes its usual meaningin the art and in HTW gasification. In preferred embodiments, thepost-gasification zone is a freeboard zone.

In certain embodiments the gasifier comprises a conical portion. Incertain embodiments, the fluidized bed zone is located within theconical portion and the post-gasification zone is located within thenon-conical portion. In certain embodiments, the conical portion isangled between 3 and 12 degrees. Having the fluidized bed zone situatedin the conical portion allows nearly constant gas velocity and uniformoxygen supply across the height of fluidized bed with the advantage ofcontrolled process conditions leading to homogeneous bubble formation inthe fluidized bed zone which enhances thereby partial oxidation andthermal decomposition of the feedstock.

The operating temperatures of the gasifier are dependent on the ashsoftening temperature of the feedstock to be gasified. Therefore, inpreferred embodiments the ash softening temperature of the feedstock tobe gasified is measured prior to operating the gasifier.

“Ash softening temperature” takes its usual meaning in the art, namelythe temperature at which particles of ash obtained from the feedstockwill begin to deform (i.e., soften) or fuse. Ash softening temperaturewhen referred to herein is measured experimentally using the standardmethod CEN/TS 15370-1.

The ash softening temperature of some example feedstocks at reducingatmosphere condition are provided below:

Ash softening temperature Feedstock type (° C.) Mix of refuse derivedfuels (RDF) and 1178 municipal solid waste (MSW) MSW 1180 RDF withplastic 1130 Untreated wood

Hard wood 1456

The above values are taken from particular feedstocks which have beentested. In general, RDF will have an ash softening temperature rangingfrom 1130 to 1230° C. and typical untreated and hard-wood from 1150 to1600° C., although impurities therein can result in ash softeningtemperatures falling outside of these ranges. The temperature ranges aretherefore merely provided as approximate ranges.

It has been identified that operating the gasifier at temperatures basedon the ash softening temperature of the feedstock results in a highlyefficient conversion of the feedstock to synthesis gas. Operating theprocess within these temperature ranges has been found to advantageouslyavoid melting the ash in the gasifier and the particles becoming sticky,which can lead to agglomerations that damage the fluidized bed.

The biomass and/or carbon-containing solid waste material feedstock (asdiscussed in detail earlier) is supplied to the gasifier (by meansdiscussed in detail earlier), preferably in pelletized form. Preferably,the feedstock is supplied to the gasifier in the fluidized bed zonei.e., via an entry point in the fluidized bed zone. In certainembodiments the feedstock is supplied to the gasifier at up to 3different entry points within the fluidized bed zone. In certainembodiments, there are 3 entry points, in other embodiments 2 entrypoints and in further embodiments only 1 entry point.

In certain embodiments, the gasification agents are supplied to thegasifier at multiple locations along the gasifier. In certainembodiments, the gasification agent is supplied to both the fluidizedbed zone and the post-gasification zone of the gasifier. In certainembodiments, the gasification agent is supplied to the gasifier atapproximately 2 to 15 locations along the gasifier, preferably 4 to 10locations, preferably 5 to 8 locations along with the gasifier.

In certain embodiments, the gasification agent is supplied to thegasifier via a plurality of nozzles. In certain embodiments, each of thenozzles are multilayered. In preferred embodiments, at least one of thenozzles is arranged at an acute angle relative to a horizontal plane ofthe gasifier. In certain embodiments, the nozzles are tuyeres. Moreinformation on the nozzles is provided below in the apparatus section.

In certain embodiments, the gasifier is operated at pressures rangingfrom about 100 to about 3000 kPa, preferably about 1000 to about 2000kPa, preferably about 1100 to about 1700 kPa, preferably about 1200 toabout 1400 kPa. In certain embodiments, the elevated pressure enables avery high production capacity in a compacted unit. In certainembodiments, the operating pressure in the gasifier is higher than about1000 kPa. In some embodiments, having an operating pressure higher thanabout 1000 kPa facilitates the post-treatment and post-processing of thesyngas at high pressure resulting in lower capital and operational costsfor typical downstream processing of syngas towards advanced fuels suchas bio-methanol.

In the process, the feedstock is contacted with a gasification agentcomprising steam and oxygen in the gasifier at the followingtemperatures:

(a) supplying the feedstock to a gasifier, the gasifier comprising afluidized bed zone and a post-gasification zone(b) between about 350-400° C. below the ash softening temperature of thefeedstock to partially oxidize the feedstock in the fluidized bed zone;(c) then at least a portion of the product of step (b) is treated at ahigher temperature, the temperature being between about 250-350° C.below the ash softening temperature of the feedstock, in the fluidizedbed zone;(d) then at least a portion of the product step (c) is treated at ahigher temperature, the temperature being between about 200-300° C.below the ash softening temperature of the feedstock, in thepost-gasification zone;(e) then at least a portion of the product of step (d) is treated at ahigher temperature, the temperature being between about 150-250° C.below the ash softening temperature of the feedstock in thepost-gasification zone.

In certain embodiments, each of the above steps takes placesubstantially in a different subzones within the gasifier. Subzonereferred to in this context refers to a zone within the fluidized bed orpost-gasification zones. In certain embodiments, each subsequent steptakes place in a subzone located above the subzone of the previous stepwithin the gasifier i.e., each step takes place progressively higher upwithin the gasifier as the feedstock rises from up the gasifier from thefluidized bed zone to the post-gasification zone until it exits thegasifier. In the gasifier, the temperature generally increases frombottom to top of the gasifier as is usual in the art. It will beunderstood that there will likely be some overlap in temperatures aroundthe borders of each subzone and hence the use of the term“substantially” above. Similarly, it will be understood that there maybe some similar overlap between the fluidized bed and post-gasificationzones.

In preferred embodiments, there is at least a 5° C., or 10° C., or 20°C., or 30° C., or 50° C. increase in temperature between each of steps(b) to (e) (i.e., between subzones B to E).

In preferred embodiments, the above temperature or thermal subzoneswithin the gasifier are generated through the controlled addition of thegasification agent. That is to say that in preferred embodiments, noexternal heat source is used. In contrast, in the preferred embodimentsthe gasification agent, comprising oxygen and steam, is injected intothe gasifier in sufficient form and amount to generate the plurality ofthermal subzones. In further preferred embodiments, the gasificationagent is injected into the gasifier in a sufficient form and amount toeffectively oxidized the feedstock and convert it into the synthesis gasproduct. In further preferred embodiments, the gasification agent isprovided in suitable form and quantity to generate the fluidisationwithin the fluidized bed zone.

In certain embodiments, operation of the gasifier also comprises a stepof cooling at least a portion of the product produced in step (e) to atemperature lower than the temperature in step (e), the temperaturebeing no greater than about 200° C. below the ash softening temperatureof the feedstock, wherein this step takes place in the post-gasificationzone, e.g. in the upper part of the post-gasification zone. In certainembodiments, the cooling step takes place in a quench subzone of thepost-gasification zone and the step of cooling is performed using quenchwater or process condensate. In preferred embodiments the cooling steptakes place in a subzone above step (d) in the post-gasification zone.In preferred embodiments, the cooling step takes place at the top of thepost-gasification zone and at the top of the gasifier. In preferredembodiments, the quench water or process condensate is injected using anozzle, preferably wherein the nozzle is located within the quenchsubzone. In certain embodiments, the temperature in this step is 200 to300° C. below the ash softening temperature of the feedstock, preferably200 to 250° C. below the ash softening temperature of the feedstock. Inpreferred embodiments, the subzone is cooled through the addition of thequench water or process condensate, preferably wherein no furtheradditional external cooling source is used.

In certain embodiments, the process further comprises a further step ofremoving at least a portion of a bottom product, such as a heavy solidresidue, produced in step (b) to a sedimentation subzone in thefluidized bed zone. In certain embodiments, the process furthercomprises treating the bottom product in the sedimentation subzone witha gasification agent comprising steam and/or CO₂. In preferredembodiments, the gasification agent comprises steam, in furtherpreferred embodiments the gasification agent is steam and/or CO₂. Incertain embodiments, the treatment is carried out at a temperature lowerthan the temperature in step (b), the temperature being not greater thanabout 400° C. below the ash softening temperature of the feedstock. Inpreferred embodiments, the temperature is between about 400° C. to 500°C. below the ash softening temperature of the feedstock. In preferredembodiments, this step takes place in a subzone below the subzone ofstep (b). In preferred embodiments, this step takes place at the bottomof the fluidized bed zone and at the bottom of the gasifier. Inpreferred embodiments, the gasification agent is injected into thissubzone in a form and quantity (in a controlled manner) to generate thetemperature and the required fluidisation within this subzone i.e., noother external heat source is used.

In preferred embodiments, the process comprises the quenching step(i.e., quenching subzone or subzone A) and bottom product removal step(i.e., sedimentation subzone or subzone F) in addition to steps (b) to(e) (i.e., subzones B to E). In this preferred embodiment the gasifiercomprises six thermal subzones, three within the fluidized bed zone andthree within the post-gasification zone.

It will be understood by the person skilled in the art that in preferredembodiments the temperature ranges referred to in the above paragraphsin relation to the steps and/or subzones which take place within thegasifier relate to average temperatures within each step and/or subzoneand that the temperature may actually be higher and/or lower in certainparts of each step and/or subzone. The use of the term “averagetemperature” herein takes it usual meaning within the art and refers tothe average temperature of each step and/or subzone and it will beunderstood that within each step and/or subzone there higher/lowertemperatures than the average will likely be present. The “averagetemperature” can be determined in accordance with methods known to theskilled person. In particular, an average temperature can be determinedby placing multiple thermocouples at different locations within asubzone in the gasifier for measuring the individual temperatures atsaid locations. In this measurement setup, the average temperature isthe mean temperature of the individual temperatures (usually the instantgas temperatures) measured by said thermocouples (by theirthermoelements) at said different locations in said subzone of thegasifier over a certain time period. In particular, if the averagetemperature remains constant the process conditions are consideredstable.

For the avoidance of doubt, in alternative embodiments the temperatureranges expressed herein may refer to absolute temperature ranges ratherthan average temperature ranges.

In certain embodiments, the particulate matter has a residence time inthe fluidized bed zone of at least about 8 minutes. Preferably, theresidence time is about 8 minutes to about 90 minutes, preferably about15 minutes to about 75 minutes, preferably about 25 minutes to about 60minutes, preferably about 35 minutes to about 45 minutes. As usedherein, the term “residence time of particulate matter in the fluidizedbed zone” may be understood as the time period from an entry of a solidmaterial into the fluidized bed to the time point said solid materialleaves the fluidized bed from the bottom of the gasifier as a bottomproduct. Said residence time can be measured by method well-known to theskilled person.

In certain embodiments, the raw synthesis gas in has a residence time inthe post-gasification zone of at least about 7 seconds, preferably atleast about 10 seconds, preferably at least about 12 seconds, preferablyat least about 15 seconds. Preferably the residence time in thepost-gasification zone is no greater than about 20 seconds, preferablyno greater than about 15, preferably no greater than about 10 seconds.The higher residence times in the post-gasification zone help to improvethe thermal decomposition of the heavier hydrocarbons, thus helping toreduce the amount of tar present in the syngas product. In particular,the term “residence time of raw synthesis gas in the post gasificationzone” may be understood as the time period from the entry of a rawsynthesis gas molecule, produced in the fluidized bed, into the postgasification zone until the exit of the raw synthesis gas molecule fromthe post-gasification zone. Said residence time can be determined bycommon methods known to the skilled person.

In preferred embodiments, an external catalyst is not added into thesystem i.e., the gasifier is operated absent the addition of external(or fresh) catalyst. This means that no external catalyst isspecifically added into the gasifier during operation. Instead, in thepreferred embodiment, the ash material within the feedstock isessentially used as the catalyst. In this respect, the bottom product ofthe present process typically contains both ash and carbon and the ashcontains a lot of different materials such as aluminum, iron, nickel,etc. which act as the catalyst. As is explained herein, it isparticularly advantageous not to have to handle and add an externalcatalyst into the process.

Recovery of the Synthesis Gas

After the raw syngas has been produced in the gasifier, it is recoveredfrom the process.

During this recovery of the synthesis gas, the raw syngas can be treatedand/or processed in accordance with any suitable treatment/processesknown in the art to refine raw syngas. These treatments typicallyinvolve removing impurities and undesired material from the raw syngas.

Such processes include, but are not limited to:

-   -   treatment in a cyclone to remove entrained dust which is        optionally recycled, in particular directly recylced, back to        the fluidized bed zone of the gasifier;    -   treatment in at least one raw gas cooler, wherein saturated        steam is optionally produced and recycled to the fluidized bed        zone of the gasifier;    -   treatment in a fly-char (dry basis) removal unit; and/or    -   treatment in a quench and scrubbing unit.

After recovering the syngas, the treated tar-free syngas can be furtherprocessed into an appropriate feedstock for production of various usefulproducts such as advanced/bio-fuels, by processes known to those skilledin the art. Such processes can offer tar-free syngas as an appropriatefeedstock to produce high valuable materials, such as methanol,synthetic natural gas and/or Fischer-Tropsch synthesis fuels.

Apparatus for Conversion of Feedstock Comprising Biomass and/orCarbon-Containing Solid Waste Material to Synthesis Gas

A schematic example of the layout of the apparatus for performing theinvention is shown in FIG. 1.

The apparatus may generally comprise any of the components and unitsshown in FIG. 1 and as described earlier on. The apparatus may alsocomprise any alternative components and units not shown in FIG. 1 butknown to be used in gasification processes. In particular, the apparatusof the invention may contain any components and units suitable forperforming the process of the invention.

In particular, the apparatus may comprise means for supplying thefeedstock to the gasifier and the gasifier itself may comprise at leastone entry point for the feedstock, preferably 1 to 3 entry points forthe feedstock. The apparatus may also comprise any means suitable forrecovering the syngas downstream of the gasifier.

As discussed earlier in the description, in certain embodiments thegasifier, which includes a fluidized bed zone and a post-gasificationzone, has a conical portion in which the fluidized bed zone is located,although the gasifier may take any suitable gasifier shape and/or form.In certain embodiments, the gasifier is a refractory lined gasifier.

In an aspect of the invention, the gasifier includes a plurality ofnozzles within the gasifier. The nozzles are configured to introduce thegasification agents into the gasifier. In particular, the nozzles areconfigured to supply in use the gasification agent so as to generateboth the required fluidisation inside the fluidized bed zone and theplurality of operating temperatures within the fluidized bed andpost-gasification zones of the gasifier. In alternative embodiments, thenozzles may be configured for other purposes. In further alternativeembodiments, the nozzles are configured to supply in use thegasification agent so as to generate the plurality of operatingtemperatures within the fluidized bed and post-gasification zones of thegasifier i.e., the plurality of temperature subzones or steps discussedearlier.

In preferred embodiments at least one of the nozzles is arranged on theside of the gasifier, although it is also possible for the nozzles to belocated at the base/bottom of the gasifier. A combination of nozzleslocated at the bottom of the gasifier and at the sides of the gasifieris also possible. In the fluidized bed zone, it is preferred that thenozzles are located at the sides of the gasifier. In preferredembodiments, a plurality of nozzles are located along the sides of thegasifier, preferably within both the fluidized bed and post-gasificationzone.

In preferred embodiments, at least one nozzle, in particular one nozzle,is configured to supply a gasification agent, such as oxygen, to thepost-gasification zone of the gasifier and is arranged in a firstsubzone of said post-gasification zone in which in step (c) of theprocess according to the present invention is carried out, i.e. insubzone D, wherein this subzone is located above, optionally directlyabove, the fluidized bed zone. Thus, said at least one nozzle arrangedin the first subzone is configured to supply gasification agent, such asoxygen, for providing an average temperature being between about200-300° C. below the ash softening temperature of the feedstock andhigher than in the fluidized be zone within this first subzone.Preferably, an outlet of said at least one nozzle is directed downwardsto the bottom of the reactor. The term “above” when used herein incontext with the gasifier refers to a relative position closer to thetop of the gasifier.

In preferred embodiments, at least one nozzle, in particular one nozzle,is configured to supply gasification agent, such as oxygen, to the postgasification zone of the gasifier and is arranged in a second subzonelocated above, in particular directly above, the above-mentioned firstsubzone in which in step (c) of the process according to the presentinvention is carried out. Said at least one nozzle is arranged in thesecond subzone where step (d) of the process of the present invention iscarried out, i.e. in subzone E. Thus, said at least one nozzle arrangedin subzone E is configured to supply gasification agent, such as oxygen,for providing the average temperature being between about 150 to 250° C.below the ash softening temperature of the feedstock and higher than inthe first subzone. Preferably, an outlet of said at least one nozzle isdirected upwards to the top of the gasifier, i.e. away from the bottomof the gasifier.

In preferred embodiments, the nozzles are located at multiple locationsalong the gasifier. In further preferred embodiments, the gasificationagents are injected through the nozzles to both the fluidized bed zoneand the post-gasification zone of the gasifier. In certain embodiments,the gasification agent is supplied to the gasifier at approximately 2 to15 locations along the gasifier, preferably 4 to 10 locations, mostpreferably 5 to 8 locations along with the gasifier.

As a person skilled in the art will understand, any arrangement ofnozzles is possible that is capable of injecting the gasification agentssuch that the plurality of temperature steps/subzones and fluidizationas required by the process of the invention is generated.

Any nozzle suitable for supplying the gasification agents to thegasifier may be used in the apparatus. Preferably the nozzles areinjection nozzles, preferably tuyeres. In certain embodiments, thenozzles may be described as lances.

In a preferred embodiment, each nozzle is a multi-layered nozzle. Incertain preferred embodiments, the nozzle is multi-layered as describedin EP 2885381 A1. In this document multi-layered nozzles are describedwhich have at least three mutually coaxial pipes, each of which delimitsat least one annular gap. The outermost pipe is designed to conductsuperheated steam and has a steam supply point, the central pipe isdesigned as an annular gap, and the innermost pipe is designed toconduct oxygen at a temperature of no higher than 180° C. and has anoxygen supply point. A temperature sensor is arranged within theinnermost pipe, said temperature sensor extending to just in front ofthe opening of the innermost pipe. The innermost pipe tapers in the formof a nozzle before opening; the innermost pipe opens into the centralpipe; and the opening of the central pipe protrudes further relative tothe opening of the outermost pipe. Thus the nozzles have a “multilayer”structure i.e., a plurality of pipes arranged coaxially to one another.

At least one of the nozzles is arranged at an acute angle relative to ahorizontal plane of the gasifier i.e., it is set at an angle relative toor away from both the horizontal plane. The term “acute angle” usedherein takes its normal meaning which is less than 90 degrees and morethan 0 degrees. The horizontal planes are defined in the normal mannerin relation to a gasifier, namely the planes perpendicular to thevertical axis of the gasifier (the vertical axis being that defined fromthe bottom to the top of the gasifier).

In essence, the at least one nozzle is configured at an angle orientatedaway from a horizontal plane of the gasifier (at an angle above or belowrelative to the horizontal plane are both possible). In preferredembodiments, the at least one nozzle may also be arranged at an acuteangle relative to a vertical plane or axis of the gasifier. In preferredembodiments, the nozzle is arranged at an angle between 5 to 85 degreesrelative to the horizontal plane, more preferred at an angle between 10to 80 degrees relative to the horizontal plane or between 20 to 60degrees relative to the horizontal plane.

In certain embodiments, more than one of the nozzles are arranged at anacute angle relative to a horizontal plane of the gasifier. In certainembodiments, all of the nozzles are arranged at an acute angle relativeto the horizontal plane i.e., all of the nozzles are configured at anangle.

It has been found that arranging the nozzles at an angle relative to thehorizontal plane of the gasifier, as well in certain embodiments usingthe preferred nozzle arrangements and multilayer configuration, enhanceslocalized transport and reaction mechanisms along the gasifier. Thisowes to the gasification agent being introduced at an acute anglerelative to the horizontal plane of the gasifier.

In particular, the angle of the nozzles provides advantages in relationto the flame (jet). Whenever oxygen (i.e., the gasification agent) isinjected into the gasifier, there is a flame observed at the outlet ofthe injection nozzle. The length of the flame should not exceed theinner radius (half of the inner diameter) of the gasifier vessel. Thisis to avoid any kind of contact between the flame tip from the injectionnozzle and a lining of the gasifier such as a refractory lining (on theother side). Therefore, the nozzles of the invention are able to havelonger flame lengths which help to enhance the cracking of highmolecular weight hydrocarbons such as naphthalene—as compared withtypical nozzles which are arranged in a horizontal plane of the gasifierand typically inject the gasification agent along a substantiallyhorizontal plane into the gasifier. Naphthalene is undesirable in theproduct synthesis gas and thus the quality of the synthesis gas productis improved.

Certain tests have also been carried out using the present process andapparatus.

Successful tests have been conducted based on the process and apparatusdescribed herein. The feedstocks tested were included the following: i)waste wood pellet (WW), ii) 75% RDF/25% WW, iii) 50% RDF/50% WW, (iv)25% RDF/75% WW and v) 100% RDF. The tests showed efficient conversion ofthe feedstock to synthesis gas, with a carbon conversion efficiency(CCE) of approximately 93-95% (wherein CCE represents the percentage oftotal carbon in the gasifier feedstock which is successfully convertedto product gases, which contain carbon (such as CO, CO₂, CH₄, C₂H₂,C₂H₄, C₂H₆, C₆H₆ and C₁₀H₈). In addition, high yields of CO and H₂ inthe range of 950-1200 Nm³/ton of dry and ash-free (daf) feedstock areachieved. The CH₄ content in the synthesis gas on a dry basis is below 8mol.-% which is indicative for the quality of the synthesis gas. On thecontrary, conventional processes (using comparable feed flow rates andcomparable feedstock) and not being carried out with a temperatureprofile (such as shown in FIG. 2) and residence times in the gasifieraccording to the invention, provide a lower carbon conversion of below90%, a yield of CO and H₂ below 800 Nm³/ton of daf feedstock and the CH₄content in the synthesis gas on a dry basis is above 12 mol.-%. Thelatter value is an indicator that tars are also present in the rawsynthesis gas of such conventional processes.

The order of the steps of the processes described herein is exemplary(unless a certain order is necessitated through the explicit wording ofthe steps), but the steps may be carried out in any suitable order, orsimultaneously where appropriate. Additionally, steps may be added orsubstituted in, or individual steps may be deleted from any of theprocesses without departing from the scope of the subject matterdescribed herein.

It will be understood that the description of preferred embodimentsherein is given by way of example only and that various modificationsmay be made by those skilled in the art. What has been described aboveincludes examples of one or more embodiments. It is, of course, notpossible to describe every conceivable modification and alteration ofthe above process and apparatus for purposes of describing theaforementioned aspects, but one of ordinary skill in the art canrecognize that many further modifications and permutations of variousaspects are possible. Accordingly, the described aspects are intended toembrace all such alterations, modifications, and variations that fallwithin the scope of the appended claims.

1. A process for converting feedstock comprising biomass and/or carbon-containing solid waste material to synthesis gas, the process comprising the following steps: (a) supplying the feedstock to a gasifier, the gasifier comprising a fluidized bed zone and a post-gasification zone; (b) contacting the feedstock with a gasification agent comprising steam and oxygen in the fluidized bed zone, at an average temperature of between about 350-400° C. below the ash softening temperature of the feedstock, to partially oxidize the feedstock; (c) contacting at least a portion of the partially oxidized product produced in step (b) with a gasification agent comprising steam and oxygen in the fluidized bed zone, at a higher average temperature than in step (b), the average temperature being between about 250-350° C. below the ash softening temperature of the feedstock; (d) contacting at least a portion of the product produced in step (c) with a gasification agent comprising steam and oxygen in the post-gasification zone, at a higher average temperature than in step (c), the average temperature being between about 200-300° C. below the ash softening temperature of the feedstock; (e) contacting at least a portion of the product produced in step (d) with a gasification agent comprising steam and oxygen in the post-gasification zone, at a higher average temperature than in step (d), the average temperature being between about 150-250° C. below the ash softening temperature of the feedstock, to produce the synthesis gas; and (f) recovering the synthesis gas from the product produced in step (e).
 2. The process of claim 1, wherein the process further comprises a step of cooling at least a portion of the product produced in step (e) to an average temperature lower than in step (e), the average temperature being no greater than about 200° C. below the ash softening temperature of the carbonaceous feedstock, wherein this step takes place in the post-gasification zone.
 3. The process of claim 2, wherein the cooling step takes place in a quench subzone of the post-gasification zone and the step of cooling is performed using quench water or process condensate.
 4. The process of claim 1, further comprising a step of removing at least a portion of a bottom product, optionally a heavy solid residue, produced in step (b) to a sedimentation subzone in the fluidized bed zone.
 5. The process of claim 4, further comprising treating the bottom product in the sedimentation subzone with a gasification agent comprising steam and/or CO₂, optionally wherein the treatment is carried out at an average temperature lower than in step (b), the average temperature being not greater than about 400° C. below the ash softening temperature of the feedstock.
 6. The process of claim 1, wherein step (f) comprises feeding at least a portion of the synthesis gas to a cyclone and separating the produced synthesis gas from entrained particulate material, optionally fly-ash or char, and recycling at least a portion of the particulate material back to step (b) in the fluidized bed zone.
 7. The process of claim 1, wherein a residence time of raw synthesis gas in the post-gasification zone is at least about 7 seconds.
 8. The process of claim 1, wherein the process comprises providing the gasification agents through a plurality of nozzles, optionally tuyeres, wherein at least one of the nozzles is arranged at an acute angle relative to a horizontal plane of the gasifier.
 9. The process of claim 1, further comprising operating the gasifier at a pressure of about 1000 kPa to 3000 kPa, optionally wherein the gasifier is a refractory lined reactor.
 10. The process of claim 1, further comprising operating the gasifier without adding external catalyst.
 11. The process of claim 1, further comprising supplying the gasification agent to the gasifier so that the oxygen content in the gasifier is in the controlled range of 0.28-0.52 Nm³/kg (daf) of the feedstock, of which at least about 20% and not greater than about 80% is supplied to the fluidized bed zone and so that the amount of steam in the gasifier is in the controlled range of 0.23-0.52 Nm³/kg (daf) of the feedstock, of which at least about 40% and not greater than about 80% is supplied to the fluidized bed zone.
 12. The process of claim 1, wherein the supplied feedstock is a pelletized feedstock, optionally further comprising pressurizing the pelletized feedstock in a pressurisation system prior to supplying the feedstock to the fluidized bed zone in step (b).
 13. The process of claim 1, wherein the post-gasification zone is arranged in the gasifier above the fluidized bed zone, wherein the fluidized bed zone is in a conical portion of the gasifier.
 14. The process of claim 1, further comprising performing each of steps (b) to (e) in substantially separate subzones within the gasifier.
 15. Apparatus for performing the process according to claim 1, wherein the apparatus comprises: a gasifier, wherein the gasifier comprises a fluidized bed zone and a post-gasification zone; and a plurality of nozzles, optionally tuyeres, within the gasifier, wherein at least one of the nozzles is arranged at an acute angle relative to a horizontal plane of the gasifier and wherein the plurality of nozzles are configured to supply in use the gasification agent so as to generate both the required fluidisation inside the fluidized bed zone and the plurality of operating temperatures within the fluidized bed and post-gasification zones of the gasifier. 